Many structures are fabricated of metal plate using joints or seams. Some such structures are petroleum storage tanks, nuclear reactor containment vessels, offshore drilling rigs and mooring towers, and water storage tanks. Some of these, and other, structures utilize welded joints deposited by submerged arc welding.
Submerged arc welding employs a mound of flux to cover the molten pool of metal formed in depositing the weld. As the weld progresses, a continuous band or stream of granular flux must be supplied to the joint to keep the weld submerged until the metal solidifies. The excess flux is then removed to complete the weld or to prepare it for deposition of the next weld pass.
Various types of equipment or apparatus has been developed for automatic girth seam, or joint, submerged arc welding of vertical plates, as see U.S. Pat. Nos. 2,638,524; 2,678,987; 2,698,891; 2,742,554; 2,761,954; 2,763,770; and 2,806,935. As shown by these patents, the granular flux is supplied to the joint by gravity and is supported by a horizontal plate or belt located beneath the joint.
In the fabrication of many structures of metal plate it is often necessary to make overhead welds on lapped joints or corner joints. These are made by hand in most instances. While overhead automatic welding has been done with the weld shielded from the atmosphere by an inert gas (i.e. argon), it is necessary to shield the weld area against air flow and wind. This is a substantial disadvantage. Furthermore, automatic submerged arc welding equipment for overhead welding is not available. A need accordingly exists for apparatus and methods for depositing submerged arc welds in overhead joints, especially automatically, so as to avoid as much as possible the use of hand welding.